Review Question - QID 203475

A 52-year-old female presents to her rheumatologist with complaints of fatigue, a sore mouth, and occasional nausea and abdominal pain over the past several months. Her medical history is significant for 'pre-diabetes' treated with diet and exercise, hypertension managed with lisinopril, and rheumatoid arthritis well-controlled with methotrexate. Her vital signs are within normal limits. Physical examination is significant for an overweight female with the findings as shown in Figures A and B. The physician orders laboratory work-up including complete blood count with peripheral blood smear as well as basic metabolic panel and serum methylmalonic acid and homocysteine levels. These tests are significant for a hematocrit of 29.5, a decreased reticulocyte count, normal serum methylmalonic acid level, increased homocysteine level, as well as the peripheral smear shown in Figure C. Which of the following could have reduced this patient's risk of developing their presenting condition?